At 2 p.m. on Wednesday, Nov. 9 the Federal Emergency Management Agency and the Federal Communications Commission will conduct the first nationwide test of the Emergency Alert System.
Participants include broadcasters, cable television systems, wireless cable systems, satellite digital audio radio service providers, and direct broadcast satellite providers. The results of this nationwide test will help assess the reliability and effectiveness of the Emergency Alert System as a public alert mechanism. During this test, the public will hear a message indicating "This is a test." This national test is anticipated to last approximately 3 minutes. This is only a test and no action or reaction is required.
You can get details about the test here: http://www.fcc.gov/encyclopedia/emergency-alert-system-nationwide-test.